Tubular heating furnace for preparing carbon nanotubes

Abstract

The utility model belongs to the technical field of preparation of carbon nanotubes, and particularly relates to a tubular heating furnace for preparing carbon nanotubes. The utility model provides a tubular heating furnace for preparing carbon nanotubes. The tubular heating furnace comprises a furnace tube and a heat insulator arranged on the periphery of the furnace tube, one end of the furnace tube is a feeding end, and the other end is a discharging end; a gap is formed between the heat insulator and the outer wall of the furnace tube and is divided into a plurality of heating cavities arranged in the length direction of the furnace tube, so that a plurality of temperature zones are correspondingly formed in the space in the furnace tube; and a heating element and a temperature detection element are arranged in the heating cavity. A plurality of air inlet pipelines are led out of the side wall of the furnace tube in the length direction of the furnace tube, and each air inlet pipeline is communicated with the interior of the furnace tube. Raw material gas is supplied through a multi-point gas inlet pipeline, the utilization rate of a carbon source can be increased, the agglomeration time of catalyst particles can be shortened, and therefore the yield of the single-walled carbon nanotubes is increased.

Description

Technical Field

[0001] The utility model belongs to the technical field of the preparation of carbon nanotubes, and particularly relates to a tubular heating furnace for preparing carbon nanotubes. Background Art

[0002] Carbon nanotubes, also known as buckytubes, are one-dimensional quantum materials with a special structure. Their radial size is on the nanometer scale, the axial size is on the micrometer scale, and both ends of the tubes are basically sealed. Carbon nanotubes are mainly composed of several to dozens of coaxial circular tubes formed by carbon atoms arranged in a hexagonal pattern. The distance between layers is fixed, about 0.34 nm, and the diameter is generally 2 - 20 nm.

[0003] According to the number of graphene layers, carbon nanotubes are divided into two categories: single-walled carbon nanotubes and multi-walled carbon nanotubes. Among them, single-walled carbon nanotubes have more advantages, specifically reflected in: simple structure, stable chemical properties, few structural defects, excellent conductivity, good elasticity, and high mechanical properties.

[0004] The production of single-walled carbon nanotubes or carbon nanotubes using some special raw materials as carbon sources is usually based on the transformation of traditional equipment such as fluidized beds, which can effectively increase the output of multi-walled carbon nanotubes. However, the output of single-walled carbon nanotubes is still relatively low, and the actual annual production capacity of a single unit is only 30 - 50 KG.

[0005] Currently, in the development and design of mass production equipment for larger-scale single-walled carbon nanotubes, there are still problems with the supply of reaction gas sources. The reaction gas sources mainly include hydrogen, carbon source gas (such as methane or other hydrocarbon gases), etc. In a traditional reaction furnace with a single inlet structure, all reaction gases (including hydrogen, carbon source gas, etc.) enter the reaction chamber through one inlet, and after entering the reaction chamber, they start to diffuse from the inlet position. The distribution state after entering the reaction chamber is greatly limited. Especially in a longer reaction furnace, this inlet method greatly affects the precise control of the gas composition around the catalyst particles, and thus affects the utilization rate of the inlet gas and the growth quality of carbon nanotubes. Summary of the Utility Model

[0006] Aiming at the deficiencies of the existing technology, the utility model provides a tubular heating furnace for preparing carbon nanotubes.

[0007] The tubular heating furnace for preparing carbon nanotubes provided by the utility model includes a furnace tube and a heat insulation body arranged on the outer periphery of the furnace tube; one end of the furnace tube is the feed end, and the other end is the discharge end; there is a gap between the heat insulation body and the outer wall of the furnace tube, and the gap is divided into a plurality of heating chambers arranged along the length direction of the furnace tube, so that the space inside the furnace tube correspondingly forms a plurality of temperature zones; heating elements and temperature detection elements are arranged in the heating chambers. A plurality of intake pipes are also led out on the side wall of the furnace tube along the length direction of the furnace tube, and each intake pipe is communicated with the inside of the furnace tube to supply raw material gas to different parts inside the furnace tube.

[0008] As a further improvement scheme of the tubular heating furnace, the heating element is an electric heating tube, and an independently controllable heating element is provided in each heating cavity to form a plurality of temperature zones with independently adjustable temperatures along the length direction of the furnace tube.

[0009] As a further improvement scheme of the tubular heating furnace, in each heating cavity, the heating elements are arranged along the length direction of the furnace tube to form two rows of symmetric heating element arrays; in each heating cavity, a temperature detection element is provided, the temperature detection element is a thermocouple, and the detection end of the thermocouple extends out from the inner wall of the heat insulation body and points to the inside of the heating cavity.

[0010] As a further improvement scheme of the tubular heating furnace, each intake pipe has a preheating section on the outer wall of the furnace tube, and the preheating section passes through the heating cavity.

[0011] As a further improvement scheme of the tubular heating furnace, a gas intake pipe is connected to the furnace tube corresponding to each temperature zone, and each gas intake pipe has an independent gas inlet end to independently control the supply of raw material gas for each temperature zone.

[0012] As a further improvement scheme of the tubular heating furnace, the tubular heating furnace further includes a cooling cover arranged outside the heat insulation body, the cooling cover includes an inner cover body that envelopes the heat insulation body and an outer cover body that envelopes the inner cover body; a cooling cavity for accommodating a cooling medium is formed between the inner cover body and the outer cover body, and a first liquid inlet and a first liquid outlet are further provided on the outer cover body; both the first liquid inlet and the first liquid outlet are communicated with the cooling cavity.

[0013] As a further improvement scheme of the tubular heating furnace, the first liquid inlet is located at the lower part of the cooling cavity, and the first liquid outlet is located at the upper part of the cooling cavity.

[0014] As a further improvement scheme of the tubular heating furnace, at the feeding end, the outer wall of the furnace tube is further wrapped with a cooling jacket, the cooling jacket can accommodate a cooling medium, a second liquid inlet is provided at the lower part of the cooling jacket, and a second liquid outlet is provided at the upper part of the cooling jacket.

[0015] As a further improvement scheme of the tubular heating furnace, a protective shell is further provided outside the cooling cover.

[0016] As a further improvement scheme of the tubular heating furnace, the protective shell blocks the periphery of the furnace tube and leaves an operation window at the feeding end of the furnace tube.

[0017] Beneficial effects

[0018] Compared with the prior art, the tubular heating furnace for preparing carbon nanotubes provided by the present utility model has the following beneficial effects in many aspects:

[0019] The design between the heating chamber and the furnace tube enables each heating chamber to independently control the temperature, forming different temperature zones during the entire reaction process, which helps to accurately control the growth temperature of carbon nanotubes at different stages and improve the yield and quality.

[0020] The raw material gas supply adopts a multi-point intake pipeline, allowing the raw material gas (such as hydrogen and carbon source) to be supplied in different temperature zones according to the requirements of different growth stages. This can not only improve the utilization rate of the carbon source but also shorten the agglomeration time of catalyst particles, thereby increasing the yield of single-walled carbon nanotubes.

[0021] The efficient cooling system helps to remove the excess heat generated during the operation of the heating furnace, protecting external equipment and the environment from the influence of high temperatures, helping to control the overall temperature distribution of the heating furnace, and ensuring the safety of operators. Description of the Drawings

[0022] Figure 1 and Figure 2 is a schematic diagram of the overall structure of the heating furnace.

[0023] Figures 3 to 6 is a schematic diagram of the internal structure of the heating furnace.

[0024] Figure 7 is a schematic diagram of the internal structure of the furnace tube.

[0025] Figure 8 is a schematic diagram of the horizontal cross-section inside the heating furnace.

[0026] Figure 9 is a schematic diagram of the structure of the feed end of the furnace tube.

[0027] Figure 10 is a schematic diagram of the structure of the collection bin.

[0028] Figure 11 is a schematic diagram of the internal structure of the collection bin.

[0029] Figure 12 is a schematic diagram of the structure of the joystick assembly.

[0030] Figure 13 is a schematic diagram of the structure of the winding roller assembly.

[0031] In the figure: 1, furnace tube; 2, heat insulator; 3, cooling hood; 4, cooling jacket; 5, protective shell; 6, collection bin; 11, intake pipe; 15, conduit; 16, atomizing nozzle; 21, heating chamber; 22, electric heating tube; 31, inner housing; 32, outer housing; 33, cooling chamber; 34, first liquid inlet; 35, first liquid outlet; 41, second liquid inlet; 42, second liquid outlet; 61, operation port; 62, flexible pipe; 63, joystick; 64, sealed bin door; 65, observation window; 66, winding roller; 67, drive motor; 111, preheating section. Detailed implementation manners

[0032] The following further clarifies the present utility model through embodiments, aiming to more clearly illustrate the technical solutions of the present utility model, rather than being construed as a limitation.

[0033] The preparation of carbon nanotubes is to perform a high-temperature reaction on raw materials containing hydrogen, catalyst precursor, growth promoter precursor, and carbon source in a heating furnace. The catalyst precursor decomposes and is reduced by collision to form catalyst particles. The carbon source decomposes on the surface of the catalyst under the action of the catalyst, dissolves into the catalyst, and then carbon caps are precipitated through diffusion. Continuous supply of the carbon source causes the carbon caps to elongate to form carbon nanotubes, which flow towards the tail end of the reaction chamber with the hydrogen gas flow, and finally form macroscopic single-walled carbon nanotubes growing in different forms such as film-like or sponge-like.

[0034] As Figures 1 to 6 A tube-type heating furnace for preparing carbon nanotubes as shown includes at least one furnace tube 1 and a heat insulator 2 arranged on the outer periphery of the furnace tube 1; the furnace tube 1 is a high-temperature-resistant pipe, which can be one or a plurality of pipes arranged in parallel. In the figure, two furnace tubes 1 are arranged in parallel in the heat insulator 2 as an example. The heat insulator 2 is made of a high-temperature-resistant heat-insulating material with low thermal conductivity, and can be integrally formed or spliced. One end of the furnace tube 1 is the feed end, and the other end is the discharge end; there is a gap between the heat insulator 2 and the outer wall of the furnace tube 1, and the gap is divided into a plurality of heating chambers 21 arranged along the length direction of the furnace tube 1, so that the space inside the furnace tube 1 correspondingly forms a plurality of temperature zones; heating elements and temperature detection elements are arranged in the heating chambers 21. Among them, the furnace tube 1 is used to accommodate reactants and provide a heating and reaction space, and the plurality of heating chambers 21 arranged between the heat insulator 2 and the furnace tube 1 can control different heating temperatures. The heating elements heat the heating chambers 21, and the temperature detection elements detect the temperature of the heating chambers 21 to provide a basis for temperature control.

[0035] In some embodiments, the catalyst precursor can be placed in a high-temperature-resistant container such as a crucible or a porcelain boat, and then the high-temperature-resistant container is placed in the furnace tube 1. In some other embodiments, the catalyst precursor can also be gradually introduced into the furnace tube 1 through a pipe with the air flow at the feed end.

[0036] In some embodiments, the carbon source gas can be introduced into the furnace tube 1 through a pipeline at the feed end. In other embodiments, the carbon source gas can also be introduced into the furnace tube 1 from a single point or multiple points on the side wall of the furnace tube 1.

[0037] Preferably, as Figure 6 and Figure 7 shown, a plurality of intake pipes 11 are also led out on the side wall of the furnace tube 1 and along the length direction of the furnace tube 1. Each intake pipe 11 is in communication with the interior of the furnace tube 1 to supply the raw material gas to different parts inside the furnace tube 1. Experiments have found that during the process of growing single-walled carbon nanotubes by the floating catalyst method, the requirements for hydrogen and the carbon source are different at different stages. The structure of multi-point intake along the side wall of the furnace tube 1 can precisely introduce the adapted raw material gas into different temperature zones at different stages, which can significantly improve the utilization rate of the carbon source. The time for the catalyst particles to agglomerate and grow is also shorter before the start of growth, thereby increasing the yield of single-walled carbon nanotubes.

[0038] Preferably, as Figure 5 and Figure 6 shown, the heating element is an electric heating tube 22, and an independently controllable heating element is provided in each heating chamber 21. As the heating element, each or each group of the electric heating tubes 22 can be independently controlled in their respective heating chambers 21, which enables the operator to precisely set different temperature zones along the length direction of the furnace tube 1, thereby optimizing the temperature conditions during the growth of carbon nanotubes and improving the quality and yield of the product.

[0039] Preferably, as Figure 5 and Figure 6 shown, in each heating chamber 21, the heating elements are arranged along the length direction of the furnace tube 1 to form two rows of symmetric heating element arrays; in each heating chamber 21, a temperature detection element is provided. The temperature detection element is a thermocouple, and the detection end of the thermocouple extends out from the inner wall of the heat insulation body 2 and points into the heating chamber 21, ensuring the accuracy and real-time nature of the temperature measurement, and further providing precise temperature feedback for temperature control.

[0040] As Figure 7 shown, each intake pipe 11 has a preheating section 111 adjacent to the outer wall of the furnace tube 1. The preheating section 111 passes through the heating chamber 21, so that the gas transported through the pipeline can be preheated before entering the furnace tube 1, thereby reducing the temperature fluctuation inside the furnace tube 1 and being beneficial to improving the reaction efficiency.

[0041] As Figure 6As shown, each furnace tube 1 is connected to an intake pipe 11 corresponding to each temperature zone. Each intake pipe 11 has an independent intake end to independently control the supply of raw material gas for each temperature zone. In this way, the supply of raw material gas can be precisely controlled according to the different requirements for the growth of carbon nanotubes in different temperature zones. This design improves the utilization efficiency of the carbon source and the growth quality of carbon nanotubes.

[0042] Preferably, as Figure 3 , Figure 4 and Figure 8 shown, the tubular heating furnace further includes a cooling cover 3 disposed outside the heat insulation body 2. The cooling cover 3 includes an inner cover body 31 that envelopes the heat insulation body 2 and an outer cover body 32 that envelopes the inner cover body 31. A cooling cavity 33 for accommodating a cooling medium is formed between the inner cover body 31 and the outer cover body 32. A first liquid inlet 34 and a first liquid outlet 35 are further provided on the outer cover body 32. Both the first liquid inlet 34 and the first liquid outlet 35 are in communication with the cooling cavity 33. An additional cooling system composed of an inner and outer double layer is added outside the heat insulation body 2. The cooling cavity 33 can accommodate the cooling medium. The cooling liquid is injected through the first liquid inlet 34 and discharged from the first liquid outlet 35 after passing through the cooling cavity 33, effectively removing the excess heat generated during the operation of the heating furnace, protecting external equipment and the environment from the influence of high temperature, and also helping to control the overall temperature distribution of the heating furnace.

[0043] Preferably, as Figure 4 shown, the first liquid inlet 34 is located at the lower part of the cooling cavity 33, and the first liquid outlet 35 is located at the upper part of the cooling cavity 33, which helps cooling media such as water and heat-conducting oil to fully cool the cooling cavity 33, promotes the circulating flow of the cooling medium, and improves the cooling efficiency.

[0044] Preferably, as Figure 6 , Figure 7 and Figure 9 shown, at the feed end, the outer wall of the furnace tube 1 is further wrapped with a cooling jacket 4. The cooling jacket 4 can accommodate a cooling medium. A second liquid inlet 41 is provided at the lower part of the cooling jacket 4, and a second liquid outlet 42 is provided at the upper part of the cooling jacket 4. The cooling medium enters from the second liquid inlet 41 at the lower part of the cooling jacket 4, absorbs the heat dissipated by the furnace tube 1, and then flows out from the second liquid outlet 42 at the upper part, which helps to reduce the temperature at the feed end and protect the safety of the operators.

[0045] Preferably, as Figure 1 and Figure 2 shown, a protective shell 5 is further provided outside the cooling cover 3. The protective shell 5 blocks the periphery of the furnace tube 1 and leaves an operation window at the feed end of the furnace tube 1.

[0046] As described above, the catalyst precursor can be placed in a high-temperature resistant container such as a crucible or a porcelain boat, and then the high-temperature resistant container is placed in the furnace tube 1. As the temperature rises, the catalyst precursor gradually volatilizes into the atmosphere in the furnace tube 1 and reacts with the raw material gas, catalyzing the carbon source to grow into carbon nanotubes in a specific arrangement. However, in this way, due to the limitations of contact and dispersion, not only is the utilization efficiency of the catalyst low, but also the catalytic activity is not fully exerted. Therefore, as Figure 7 shown, a conduit 15 extending into the furnace tube 1 is provided at the feed end of the furnace tube 1, and an atomizing nozzle 16 is connected to the end of the conduit 15 inside the furnace tube 1. The catalyst precursor can be evenly dispersed into the reaction atmosphere in the furnace tube 1 through the atomizing nozzle, increasing the contact between the catalyst and the raw material gas, thereby promoting a more effective catalytic reaction and promoting the efficient and uniform growth of carbon nanotubes. On the other hand, the catalyst precursor is preheated during the flow in the furnace tube 1, reducing agglomeration and providing more active sites, realizing the growth of high-efficiency and high-purity single-walled carbon nanotubes.

[0047] Preferably, the atomizing nozzle 16 is located within a temperature zone near the feed end.

[0048] Preferably, as Figure 9 shown, the feed end of the furnace tube 1 has a flange port, and a sealing connection plate is provided on the conduit 15. The flange port at the feed end of the furnace tube 1 is detachably connected to the sealing connection plate on the conduit 15, for example, through connecting parts such as bolts and clamps to achieve detachable connection.

[0049] Based on the floating catalyst chemical vapor deposition method, the grown single-walled carbon nanotubes are flocculent, light in material and large in volume, and are easily adhered to the low-temperature zone of the reaction chamber, causing blockage of the furnace tube 1, increasing the pressure in the furnace, and affecting the continuity and safety of production.

[0050] As Figure 1 , Figure 10 , Figure 11 and Figure 12 shown, at the discharge end of the tube furnace, a carbon nanotube discharge device is provided. The discharge device includes a collection bin 6. The interior of the collection bin 6 has a collection cavity communicating with the discharge port of the tube furnace, that is, the furnace tube 1 communicates with the collection bin 6; an operation port 61 is provided on the collection bin 6, and a flexible pipe 62 is connected to the operation port 61, and the operation port 61 is hermetically connected to the proximal end of the flexible pipe 62; at least one operating rod 63 passes through the flexible pipe 62 and extends into the collection cavity, and the distal end of the flexible pipe 62 is hermetically connected to the operating rod 63; a discharge interface is provided at the bottom of the collection bin 6.

[0051] This discharging device is provided with a collection bin 6 at the discharging port of the furnace tube 1. The operation port 61 is connected by a flexible pipe 62 to at least one operating rod 63 extending into the interior of the collection bin, allowing the operator to safely transfer and collect the flocculent single-walled carbon nanotubes that are likely to cause blockage of the furnace tube during the growth process outside. In addition, a transfer tank can be connected at the discharging interface. When the flocculent carbon nanotubes in the collection bin 6 accumulate to a certain amount, the operator can use the operating rod 63 to dial the flocculent material into the transfer tank, and then cut off the connection between the discharging interface and the transfer tank, and replace it with a new transfer tank. In this way, the operation of the heating furnace is not affected during the operation, and discharging can be achieved without affecting continuous production, thus solving the problems of continuous production and safety, and improving the mass production capacity of single-walled carbon nanotubes.

[0052] Preferably, the flexible pipe 62 is an elastic corrugated pipe made of metal. The elastic corrugated pipe made of metal not only has good high-temperature resistance and can withstand the high-temperature environment during the operation of the heating furnace, but also has good flexibility and extensibility, can adapt to the position adjustment or slight movement of the collection bin 6, and at the same time allows the operating rod 63 to have a large space for linear movement and rotational movement during the operation. Metal corrugated pipes usually also have high mechanical strength and durability, can effectively prevent deformation or rupture caused by external pressure changes, and ensure the safety and stability of the operation.

[0053] As Figure 12 shown, the sizes of the distal end and the proximal end of the flexible pipe 62 can be the same, forming a pipe with a substantially uniform diameter. More preferably, the size of the proximal end of the flexible pipe 62 can be larger than that of the distal end, forming a flared shape, so that the operating rod 63 can obtain a larger operating space and improve the flexibility of the operating rod 63.

[0054] Preferably, as Figure 12 shown, the end of the operation port 61 has a flange, and the proximal end of the flexible pipe 62 has a flange. The flange at the end of the operation port 61 is detachably connected to the flange at the proximal end of the flexible pipe 62. For example, the detachable connection can be achieved through connecting parts such as bolts and clamps, which not only ensures the sealing performance, but also enables the operating rod 63 to be easily replaced or taken out as needed, enhancing the operation flexibility of the equipment.

[0055] Preferably, as Figure 12 shown, the distal end of the operation port 61 has a flange, and a sealing connection plate is provided on the rod body of the operating rod 63. The flange at the distal end of the operation port 61 is detachably connected to the sealing connection plate on the operating rod 63. Similarly, the detachable connection can also be achieved through connecting parts such as bolts and clamps, which is convenient for quick assembly and disassembly, and is convenient for maintenance and cleaning.

[0056] Preferably, as Figure 12As shown in the figure, one end of the joystick 63 located inside the collection bin 6 has a hook, and the end of the joystick 63 located outside the collection bin 6 has a handle. The hook part at the front end of the joystick 63 can be used to hook or move the carbon nanotube flocs inside the collection bin 6, while the handle facilitates the operator to apply force outside the collection bin 6 to control the movement of the joystick 63, improving the operation convenience and safety.

[0057] Preferably, as Figure 11 shown, the bottom of the collection bin 6 is conical and is provided with a discharge port at the bottom; a sealing door 64 is provided on one side of the collection bin 6 opposite to the discharge port of the tubular heating furnace, and an operation port 61 is provided on the sealing door 64.

[0058] Preferably, as Figure 11 shown, at least one observation window 65 is further provided on the collection bin 6, and the observation window 65 and the operation port 61 are located on the same side of the collection bin 6.

[0059] Preferably, as Figure 11 and Figure 13 shown, a winding roller 66 is rotatably provided inside the collection bin 6, and the winding roller 66 is driven to rotate by a driving motor 67 installed on the outer side wall of the collection bin 6. In this way, the prepared carbon nanotube flocs can be wound on the roller orderly, avoiding the accumulation and chaos of materials. After winding, it is also convenient for the joystick 63 to pick off the carbon nanotube flocs as a whole, facilitating full collection, and improving the collection efficiency and cleanliness.

[0060] Preferably, as Figure 11 shown, there is a sandwich space inside the wall of the collection bin 6, and a circulating cooling medium can be maintained in the sandwich space to prevent the temperature of the outer wall of the collection bin 6 from being too high.

[0061] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and characteristics of the present invention, so that those skilled in this field can understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A tubular heating furnace for preparing carbon nanotubes, characterized in that: The invention comprises a furnace tube (1) and a heat insulator (2) arranged on the outer periphery of the furnace tube (1); one end of the furnace tube (1) is a feed end, and the other end is a discharge end; there is a gap between the heat insulator (2) and the outer wall of the furnace tube (1), and the gap is divided into a plurality of heating chambers (21) arranged along the length direction of the furnace tube (1), so that the space inside the furnace tube (1) forms a plurality of temperature zones; a heating element and a temperature detection element are arranged in the heating chamber (21); A plurality of air inlet pipes (11) are extended from the side wall of the furnace tube (1) and along the length direction of the furnace tube (1), and each of the air inlet pipes (11) is connected to the interior of the furnace tube (1) so as to supply raw gas to different parts of the furnace tube (1).

2. The tubular heating furnace for preparing carbon nanotubes according to claim 1, characterized in that: The heating element is an electric heating tube (22), and each heating chamber (21) is provided with an independently controllable heating element, so as to form a plurality of independently adjustable temperature zones along the length direction of the furnace tube (1).

3. The tubular heating furnace for preparing carbon nanotubes according to claim 2, characterized in that: In each of the heating chambers (21), the heating elements are arranged along the length direction of the furnace tube (1) to form two rows of symmetrical heating element arrays; in each of the heating chambers (21), a temperature detection element is provided, the temperature detection element being a thermocouple, the detection end of the thermocouple protruding from the inner wall of the heat insulating body (2) and pointing into the heating chamber (21).

4. The tubular heating furnace for preparing carbon nanotubes according to any one of claims 1 to 3, characterized in that: Each of the air inlet pipes (11) has a preheating section (111) on the outer wall of the furnace tube (1), and the preheating section (111) passes through the heating chamber (21).

5. The tubular heating furnace for preparing carbon nanotubes according to claim 4, characterized in that: The furnace tube (1) is connected to an air inlet pipe (11) corresponding to each temperature zone, and each air inlet pipe (11) has an independent air inlet end to independently control the supply of raw gas to each temperature zone.

6. The tubular heating furnace for preparing carbon nanotubes according to claim 4, characterized in that: The tubular heating furnace further comprises a cooling hood (3) arranged outside the heat insulating body (2), the cooling hood (3) comprising an inner hood (31) enveloping the heat insulating body (2) and an outer hood (32) enveloping the inner hood (31); a cooling cavity (33) for accommodating a cooling medium is formed between the inner hood (31) and the outer hood (32); a first liquid inlet (34) and a first liquid outlet (35) are further provided on the outer hood (32); the first liquid inlet (34) and the first liquid outlet (35) are both in communication with the cooling cavity (33).

7. The tubular heating furnace for preparing carbon nanotubes according to claim 6, characterized in that: The first liquid inlet (34) is located at the lower part of the cooling cavity (33), and the first liquid outlet (35) is located at the upper part of the cooling cavity (33).

8. The tubular heating furnace for preparing carbon nanotubes according to claim 4, characterized in that: At the feed end, the outer wall of the furnace tube (1) is also wrapped with a cooling jacket (4), the cooling jacket (4) can accommodate a cooling medium, a second liquid inlet (41) is provided at the lower part of the cooling jacket (4), and a second liquid outlet (42) is provided at the upper part of the cooling jacket (4).

9. The tubular heating furnace for preparing carbon nanotubes according to claim 6, characterized in that: A protective shell (5) is also provided outside the cooling cover (3).

10. The tubular heating furnace for preparing carbon nanotubes according to claim 9, characterized in that: The protective shell (5) blocks the peripheral side of the furnace tube (1) and leaves an operation window at the feed end of the furnace tube (1).

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